Healthy rivers need diversity, too

Savvy financial investors know that a diverse portfolio generates stability due to a balance of ups and downs across investments. A similar hypothesis posits that larger river systems offer similar stability to their ecosystems. Moore et al. tested this hypothesis in one of the few remaining free-flowing river systems in North America, the Fraser River watershed. They found that larger watersheds were more stable in terms of water temperature and flow, and produced salmon more consistently. This shows that greater biological diversity can buffer ecosystems against environmental variability and may enhance long-term stability.

Ecol. Soc. Am. 10.1890/14-0326.1 (2014).

Climate Change

Another cause of climate change is developing

H. Jesse Smith

The continuing increase in greenhouse gas concentrations is not the only thing driving global warming; changing land use, such as the conversion of forests to farmland, is adding to the problem, too. Because increasing population and rising affluence will require more land be farmed in order to supply food to the world, our climate will experience even more disruption in the coming decades. Ward et al. calculate the climate forcing due to land use and land cover change and find that it is contributing nearly half as much as anthropogenic greenhouse gas emissions, and that could grow in the future. Their work shows how important land policy will be in efforts to minimize continued climate warming.

Atmos. Chem. Phys. 10.5194/acp-14-12701-2014 (2014).

Cancer Biology

Engineering cancer cell metastasis

Paula A. Kiberstis

Cancer cell metastasis is not random. Breast cancer, for example, tends to metastasize to bone. To explore what underlies this selectivity, Jeon et al. took an engineering approach: They built in vitro microfluidic models that allowed them to compare how different tissue microenvironments affect the ability of breast cancer cells to exit blood vessels (extravasate) and enter surrounding tissue. They found that a bone-mimicking microenvironment was particularly potent in inducing extravasation. Adding the nucleoside adenosine to the system, which binds to breast cancer cells, reduced their extravasation, suggesting that this model might be a valuable way to screen for drugs that block metastasis.

Proc. Natl. Acad. Sci. U.S.A.112, 214 (2015).

Aging

The downside of living a longer life

L. Bryan Ray

Over the years, scientists have identified many factors that increase longevity in animal models. But do these interventions also let animals stay healthy longer, giving them an extended “healthspan”? To find out, Bansal et al. measured a range of physiological parameters over the lifetime of worms with mutations that extended their lifespans. The effect of these mutations on healthspan was variable. In fact, control worms had the greatest healthspan when calculated as a percentage of total lifespan. Extending the period of ill health of an increasingly aged human population could be devastating, suggesting that researchers should focus on optimizing healthspan rather than lifespan.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1412192112 (2015).

Solid-State Physics

Engineering a copper oxide look-alike

Jelena Stajic

Many discoveries of spectacular material properties are serendipitous. Scientists can make the discovery process more predictable if they design materials from the “bottom up” to behave in a certain way. Disa et al. fabricated heterostructures consisting of alternating layers of LaTiO3, LaNiO3, and LaAlO3, with the aim of making a material in which the top two valence orbitals are filled with electrons to very different degrees. This property can lead to exotic effects and may be useful for making high temperature copper oxide superconductors. The authors used x-ray absorption spectroscopy to verify the properties of the heterostructure. Their theoretical calculations showed that replacing LaAlO3 with a different material can lead to further improvements.

Phys. Rev. Lett. 10.1103/PhysRevLett.114.026801 (2015).

Organic Chemistry

Olefins from seed oils at industrial scales

Linear-chain olefins with terminal double bonds (linear α-olefins, or LAOs) are essential building blocks for both commodity products, such as lubricants and thermoplastics, and fine chemicals and drugs. Many fatty acids derived from seed oils have a linear tail containing a central double bond, and exchanging this tail with ethylene (ethenolysis) would provide a renewable source of LAOs. However, most catalysts for this reaction deactivate after thousands of reaction cycles (turnovers) and require unacceptable amounts of catalyst. Marx et al. now report a ruthenium ethenolysis catalyst bearing a cyclic alkyl amino carbene ligand that achieves more than 100,000 turnovers at a catalyst loading of only three parts per million.

Angew. Chem. Int. Ed. 10.1002/anie.201410797 (2014).

Symbiosis

What's mine is yours, and what's yours is mine

Caroline Ash

Pea aphids require the bacterium Buchnera to develop and reproduce

PHOTO: SHIPHER WU

Many invertebrates harbor symbiotic bacteria. Because these relationships have evolved over millions of years, dissecting whether a particular feature of an organism results from the host's or the symbiont's genes is a challenge. Moran and Yun discovered how to manipulate an obligatory symbiosis between a bacterium and its aphid host. They did this by exploiting a natural mutation in the bacteria that causes them to die at high temperatures. They then replaced the dead bacteria by injecting heat-tolerant bacteria. Evidence of success came when not just the symbionts but also the recipient aphids developed a striking tolerance to high temperatures.